Desenvolvimento e caracterização de revestimentos comestíveis a partir de farinha de casca de banana (Musa spp.) Prata (AAB)

Abstract

The agricultural and food processing industries generate amount of waste that can cause environmental problems. However, these residues have represented an alternative for the substitution of non-biodegradable plastic polymers. Thus, this study had as objective the development of edible coatings from the use of ripe banana peel of the variety Prata. In the first stage of the work, mature banana peel flour was elaborated and characterized as to its chemical composition, phenolic compounds and antioxidant activity. The flour presented as a homogeneous brown powder, with moisture content (6,48%) in accordance with the legislation, and glycolic composition (25,04%) suitable for ripening mature fruit. The lipid contents (14,42%) and total fibers were expressive, with emphasis on the insoluble fibers (37,32%). By the extractive method, 83,05 ± 12,46 GAE.100 g-1 flour was extracted. The antioxidant capacity of the flour was analyzed by the ABTS+ free radical capture methods, iron reduction power and DPPH free radical capture, presenting the respective values 8,46 M Trolox/g, 12,73 M ferrous sulfate/g and 11,31 M Trolox/g. In the second stage of the work, films from the banana peel flour were elaborated according to the Rotational Compound Central Design, varying the starch concentration and the heating time, being characterized in physical, mechanical and barrier properties. The films obtained presented a thickness varying between 0,059 and 0,085 mm, influenced by the starch concentration. As for the colorimetric parameters, the chroma showed to be dependent on the starch concentration and heating time, and the luminosity had an inverse behavior to the heating time; the tonality was not affected by the variables. The films presented solubility values between 27,35 and 43,83%, showing no tendency in relation to the studied variables. The films expressed water vapor permeability values ranging from 0,33 to 0,55 g/h.m.Pa, being influenced by the increase of the starch concentration. As for the mechanical behavior, the films showed tensile strength between 0,14 and 0,70 MPa, and together with the elastic modulus (3,00 to 33,08 MPa), presented a relation with the starch concentration; already the elongation rates were influenced by the heating time, varying between 9,84 and 20,16%. The drilling test (5,56 to 20,01 MPa) was influenced by the two dependent variables, and the strain rates (9,05 to 30,13%) were influenced by the dependent variables and their interaction. The films with the best characterization results were analyzed for centesimal composition, phenolic compounds and antioxidant activity. These films had a significant content of total carbohydrates (60,33%), significant fiber content (8,92% for insoluble fibers and 5,20% for solubles) and moderate moisture content (19,03%). The flour contributed with a proportion of minerals to the final composition of the films, not occurring the same with lipids and proteins. The content of phenolic compounds and the antioxidant activity of the films remained stable even after processing. The coatings presented an acceptable degree of plasticization, being favored by the final moisture content and the intermolecular interactions between the components of flour, starch and glycerol.